The invention is based on an apparatus for sterilizing, filling and sealing containers. Before being put into operation each time, the individual chambers as well as the filling and sealing devices built into them in such apparatus are sterilized by having a sterilizing agent in gaseous or vapor form, such as a mixture of hydrogen peroxide and air, flow through them and act on them for a predetermined period of time. To that end, the device for feeding the sterilizing agent into and through the chambers is designed so as to have the sterilizing agent flow in one direction through the chambers in succession. It sometimes happens that in corners reached only poorly by the sterilizing agent, germs will survive and will get into containers and into the product to be placed in them.